The present invention relates to an endoscope apparatus which can perform special light observation using broadband light, such as white illumination light, and specific narrowband light.
In recent years, an endoscope apparatus which can perform so-called special light observation which irradiates specific narrow wavelength band light (narrowband light) onto a mucosal tissue of a living body and acquires tissue information at a desired depth of the body tissue is utilized. This type of endoscope apparatus can simply visualize living body information which is not acquired in, for example, normal observation images, such as enhancement of the surface layer fine structure of a new blood vessel generated in a mucosal layer or a submucosal layer, and a lesional part. For example, when an observation target is a cancerous lesional part, a fine blood vessel of a tissue surface layer or the state of fine structure can be observed in more detail if blue (B) narrowband light is irradiated on a mucosal tissue. Therefore, the lesional part can be more exactly diagnosed.
Even in this special light observation as well as the normal light (broadband light) observation, it is necessary to perform white balance processing on an acquired captured image in order to stabilize the reproducibility of color tone and to perform more exact diagnosis.
JP 2006-68321 A discloses an endoscope apparatus which can perform white balance processing in a short time in the normal light observation and the special light observation, respectively.
In the special light observation, when the distance between a diseased tissue and the irradiation position of the special light is short, a fine blood vessel or fine structure of a tissue surface layer which can be brightly viewed without difficulty can be imaged. However, there is a problem in that, as the distance increases, a captured image becomes dark and is not easily seen. Generally, a measure for increasing irradiation light quantity is taken. However, there is a limit to an increase in the irradiation light quantity, particularly, an increase in the light quantity of special light. There is a problem in that, if an attempt to compensate for the shortage of the light quantity of special light with normal light is made, the tint of a captured image changes.